KR20170133383A - Modified cellulose ether with improved workability for use in plaster smoothed mortar and joint filler applications - Google Patents

Abstract

The present invention provides an additive for a dry mix or a tape joint compound composition comprising at least one cellulose ether powder containing a polymeric additive selected from a polymeric colloidal stabilizer, a polymeric fluidizer and combinations thereof on the surface. Wherein the additive is selected from the group consisting of a polymeric colloidal stabilizer and a polymeric fluidizer in an amount of from 0.1 to 10% by weight, based on the total cellulose ether solids, of a wet cellulosic ether mixture containing 60 to 80% And combinations thereof to form an additive; The additive is dried and ground; And the additive is combined with 0.1 to 20% by weight of the dry polyacrylamide based on the total cellulose ether solids.

Description

Modified cellulose ether with improved workability for use in plaster smoothed mortar and joint filler applications

The present invention relates to a process for the preparation of polymeric stabilizers, such as wet cellulosic ethers and polymeric colloidal stabilizers, for example polyvinyl alcohol, and polymeric fluidizers, such as polycarboxylate ethers, at elevated temperatures, To a dry mixture containing a composition prepared by the process of the present invention as well as a method for preparing a composition for use as a dry mix additive, comprising kneading a polymer additive selected from the combination.

The compressive and flexural strength as well as the workability are very important for gypsum or plaster surfaces and for gypsum-smoothed mortar and joint filler compositions used to finish sheet rock or gypsum plate joints and surface irregularities, respectively Performance criteria. When combined with water or moisture, lumps are formed in such compositions by the very fine gypsum particle size provided (less than 315 [mu] m (not more than 1% by weight retained on a 200 [mu] m sieve (DIN EN 13963 (2011-11) Avoiding lump formation is important in the context of workability. Curing to constant compression and bending strength is important in the context of the final properties of the material.

To improve the workability of gypsum-smoothed mortars and joint fillers, a known approach involves blending dry cellulosic ethers with polyacrylamides. Alternative additives such as water reducing agents (super plasticizers) or polycarboxylate dispersant polymers have also been used. For example, the use of calcium lignin sulfonate as a super plasticizer for modifying a thickening agent-containing methylcellulose composition to improve workability is disclosed in Aqualon GmbH "Cellulose derivatives, thickeners and fluidizers, German patent DE3920025A1 for " additive mixture "is known. However, the workability of such gypsum-smoothed mortar and tape joints, dry mixes and liquid compositions used, in particular in terms of naturally occurring inconsistency, especially in gypsum, still needs improvement.

The present invention addresses the problem by providing a gypsum-smoothed mortar and tape joint compound with improved workability as mortar and improved compression and bending strength upon curing.

1. According to the present invention, a process for the preparation of a composition for use as a gypsum dry mixture or liquid tape joint compound additive is carried out at a temperature of from 50 to 120 DEG C or, preferably, from 60 to 80 DEG C, 0.1 to 10% by weight, or preferably 0.2 to 5% by weight, or more preferably 0.1 to 10% by weight, based on the total cellulose ether solids, of one or more cellulose ethers, preferably hydroxyethyl methylcellulose or methylcellulose, and total cellulose ether solids , Preferably 0.3 to 5% by weight, of a polymeric colloidal stabilizer, preferably polyvinyl alcohol, and a polymeric fluidizer, such as a super plasticizer, preferably a polycarboxylate ether, or, more preferably, Polyacrylic acid or polymethacrylic acid containing at least one alkyl polyglycol ether side chain, and combinations thereof. By kneading the wet cellulose ether mixture containing bots additives to form an additive; The additive is dried and the average particle size of at least 25 wt.% Is measured to be <63 μm (measured by light scattering) or, preferably, at least 30 wt% &Lt; / RTI &gt; The additive is combined with one or more dry polyacrylamides of from 0.1 to 20% by weight, or preferably from 0.1 to 4% by weight, based on the total cellulose ether solids.

2. According to the method of item 1 above, the kneading device is an extruder such as a single-screw extruder or a multi-screw extruder; Kneader; Banbury Mixer; Such as an IKA high shear mixer, an Oakes rotor stator mixer, a Ross mixer, a Silverson mixer, a continuous high shear mixer; Or a homogenizer.

3. The method according to any one of the above items 1 or 2, wherein the polymer additive is a polymeric fluidizing agent as an aqueous composition having 10 to 50 wt% solids.

4. The method of any one of claims 1, 2, or 3, wherein the polymer additive is a polymeric fluidizer selected from a polycarboxylate ether, and a melamine / formaldehyde sulfonate.

5. The polymeric additive according to any one of the above items 1 and 2, wherein the polymeric additive is a polymeric colloidal stabilizer as an aqueous composition having 5 to 30 wt% solids.

6. In another embodiment of the present invention,

Gypsum or calcium sulfate; And (i) from 0.1 to 10% by weight, or preferably from 0.2 to 5% by weight, or more preferably from 0.3 to 5% by weight, based on the total cellulose ether solids, of a polymeric colloidal stabilizer, Polyvinyl alcohol and a polymeric fluidizer such as a super plasticizer, preferably a polycarboxylate ether, or, more preferably, a polyacrylic acid or polymethacrylate containing one or more alkyl polyglycol ether side chains (Ii) from 0.1 to 20% by weight, or preferably from 0.1 to 4% by weight, based on the total cellulose ether solids, of at least one cellulose ether powder comprising, on its surface, a polymeric additive selected from Of a dry mix additive which further comprises a polyacrylamide.

7. The dry mixture composition of item 6, wherein the gypsum or calcium sulfate is substantially free of calcium sulfate hemi-hydrate.

8. The dry mix composition according to item 6 or 7 above, further comprising at least one inorganic filler such as talc or calcium deoxygenate.

9. The dry mix composition of any one of the above items 6, 7 or 8, further comprising at least one water redispersible polymer powder of an emulsion polymer such as an acrylic emulsion polymer or a vinyl ester emulsion polymer such as ethylene-vinyl acetate do.

10. The dry mix composition of any one of the above items 6, 7, 8, or 9, wherein the dry mix additive has an average particle size < 63 micrometers (measured by light scattering) of at least 25 wt% Is a powder having an average particle size of at least 30 wt% < 63 mu m (as measured by light scattering).

Unless otherwise stated, all temperature and pressure units are room temperature and standard pressure (STP).

All phrases including parentheses refer to either or both of the enclosed parentheses content or its absence. For example, the phrase "(meth) acrylate" alternatively includes acrylate and methacrylate.

All quoted ranges are inclusive and combinable. For example, the contents of 50 to 120 占 폚 or preferably 60 to 100 占 폚 may be used at a temperature of 50 to 120 占 폚, 50 to 60 占 폚, 60 to 120 占 폚, 100 to 120 占 폚, 50 to 100 占 폚, Lt; RTI ID = 0.0 &gt; 100 C, &lt; / RTI &gt;

As used herein, " aqueous "means that the continuous phase is water-miscible compound (s) from 0 to 10% by weight, based on the weight of the medium. Water is preferred.

As used herein, the phrase "on a total solids basis" refers to any amount of any non-volatile component in the aqueous composition, such as synthetic polymer, cellulose ether, filler, other inorganic materials, Refers to the amount of weight of the ingredients presented.

The term "DIN EN" as used herein refers to the English version of the German material standard (Alleinverkauf) published by Beuth Verlag GmbH of Berlin, Germany. And, the term "DIN " as used herein refers to the German version of the same material specification.

As used herein, "dry mix" means a powder that is stable to storage, containing gypsum, cellulose ethers, optional polymer additives, and optional fillers and dry additives. There is no water in the dry mixture; Therefore, it is stable to storage.

As used herein, "substantially free of calcium sulfate hemi-hydrate" means that the level of calcium sulfate hemi-hydrate is less than 1 wt%, preferably less than 0.5 wt%, more preferably less than 1 wt%, based on the weight of the gypsum or calcium sulfate solids Means less than 0.1% by weight.

When a polymeric fluidizer, for example, a super plasticizer, is kneaded at high temperature together with cellulose ether, the workability of the resulting gypsum-containing product or mortar is drastically improved. In addition, when a polymeric colloidal stabilizer such as polyvinyl alcohol (PVOH) is kneaded together with cellulose ether at a high temperature, the warpage and compressive strength of the resulting gypsum-containing cured material are drastically improved. In the present invention, cellulose ethers coated with a polymer additive, such as HEMC, particles or domains, are obtained by this method. The workability of the gypsum mortar is not affected by the addition of PVOH; Any agglomeration problems caused by modifiers, such as polymeric colloidal stabilizers, are avoided. The incorporated polymeric fluidizer, e. G., Super plasticizer, does not exhibit a negative effect on the cured gypsum mortar; Thus, the measured values for compression and flexural strength are comparable to those of cellulose ethers such as HEMC when used in conventional manner.

During kneading, the moisture content in the kneading device should be in the range of from 60 to 80% by weight of the mixture to be kneaded so as to maintain the proper pressure to perform kneading and prevent damage to the kneader or its contents.

During kneading, the temperature of the contents in the kneader should be maintained at a high temperature to enable improved mixing and should not exceed the gelation point of the cellulose ether to prevent agglomeration. Since the kneading is continued for a short time period, the content in the kneader does not exceed the gelation point of the cellulose ether during kneading, and the kneader itself can be set at a temperature which sufficiently exceeds the gelation point of the cellulose ether.

The kneading can be continued for 10 to 120 minutes, or preferably 20 to 60 minutes. The kneading can be carried out in 1, 2 or more steps.

Any cellulose ether that is soluble in water at &lt; RTI ID = 0.0 &gt; 20 C &lt; / RTI &gt; In such compounds, the hydroxyl groups present in the cellulose may be partially or wholly substituted with -OR groups, wherein R is (C ₁ -C ₆ ) Alkyl group, a hydroxy (C ₁ -C ₆ ) alkyl group, and mixtures thereof. The presence of alkyl substitution in cellulose ethers is commonly described by DS, i.e. the average number of OH groups substituted per anhydroglucose unit. For example, the methyl substitution is specified by DS (methyl) or DS (M). Similarly, the presence of a hydroxyalkyl substitution is typically described as the average number of moles of esterification reagent bound in an ether-like manner per MS, i.e., anhydroglucose unit mole. For example, etherification with ethylene oxide is described as MS (hydroxyethyl) or MS (HE), and etherification with propylene oxide as MS (hydroxypropyl) or MS (HP). The determination of DS and MS is described, for example, in PW Morgan, Ind . Eng. Chem . Anal. Ed. 18 (1946) 500-504, and RU Lemieux, CB Purves, Can. J. Res. Sect. B 25 (1947) 485-489.

Suitable cellulose ethers for use in the process of the present invention may include, for example, hydroxyalkylcellulose or alkylcellulose, or mixtures of such cellulose ethers. Examples of suitable cellulose ether compounds for use in the present invention include, but are not limited to, methylcellulose (MC), ethylcellulose, propylcellulose, butylcellulose, hydroxyethylmethylcellulose (HEMC), hydroxypropylmethylcellulose (HPMC) , Hydroxyethylcellulose ("HEC"), ethylhydroxyethylcellulose (EHEC), methylethylhydroxyethylcellulose (MEHEC), hydrophobically modified ethylhydroxyethylcellulose (HMEHEC), hydrophobically modified hydroxyethyl Cellulose (HMHEC), sulfoethylmethylhydroxyethylcellulose (SEMHEC), sulfoethylmethylhydroxypropylcellulose (SEMHPC), and sulfoethylhydroxyethylcellulose (SEHEC). Preferably, the cellulose ether is a binary mixed ether such as hydroxyethyl methylcellulose ("HEMC"), hydroxypropylmethylcellulose ("HPMC") and ethylhydroxyethylcellulose.

Suitable polymeric fluidizers for use in the process of the present invention include any polycarboxylate ether (PCE), such as a carboxylate salt polymer with long polyethylene glycol side chains, and water soluble polycondensation products of fatty acids, dialkanolamines and maleic anhydrides, Lignin sulfonates, condensation products of melamine / formaldehyde sulfonates, naphthalene sulfonic acid / formaldehyde condensates containing sulfonate or sulfonic acid groups, and aryl sulfonic acid-formaldehyde condensation products. Suitable polymeric fluidizers include those sold under the trade name Glenium ^TM 51 esterified methyl polyethylene glycol side chain polymethacrylic acid polycarboxylate or the Meltem ^TM sulfonated melamine / formaldehyde resin condensate (both BASF, Ludwigshafen, Germany) Lt; / RTI &gt; product).

Suitable polymeric colloidal stabilizers for use in the process of the present invention may include polyvinyl alcohol (PVOH) and polyvinyl alcohol-co-vinyl ester copolymers. PVOH can be prepared, for example, by polymerizing vinyl acetate and then partially hydrolyzing the ester group by alkali hydrolysis to hydrolyze some or all of the ester groups.

Suitable polyacrylamide polymers for use in the process of the present invention may be polymers of acrylamide, methacrylamide, N-methylacrylamide, N, N-dimethylacrylamide. Preferred acrylamides have GPC (pAA) weight average molecular weights ranging from 1 to several million. The non-ionic polyacrylamide compound preferably has an average molecular weight in the range of about 1 to 3 million and the preferred cationically modified polyacrylamide compound has a weight average molecular weight in the range of about 3 to 5 million, The modified polyacrylamide compound is preferably present in an average molecular weight range ranging from 1 to several million.

In general, there are two types of tape joint compounds or gypsum mortar: 1) dry type and 2) setting. Both of these generally comprise gypsum, and further comprise one or more fillers.

The dry-type composition may be provided as a dry-mix composition ready for use or as a liquid-tape joint compound, and is an inorganic filler predominantly of calcium carbonate or limestone. For storage, water can be mixed with inorganic fillers but does not react with inorganic fillers. In application, water evaporates into the atmosphere.

The curable composition may be sold as a dry mixture powder and water should not be added until used in the working position, otherwise the dry mixture will be agglomerated in the wrapper and become useless. The primary inorganic filler is calcium sulfate hemi-hydrate and the water reacts with the filler and is therefore the term hardenable. Preferably, the composition of the present invention is a dry-type composition and is a tape joint or a gypsum-smoothing compound (liquid) composition or a dry-mix composition.

The dry mix and the liquid composition of the present invention may comprise at least 10 wt%, preferably at least 40 wt%, or even more preferably at least 60 wt%, based on the total dry weight of the composition, Lt; RTI ID = 0.0 &gt; 80% &lt; / RTI &gt; by weight.

The composition of the present invention may comprise an inorganic filler. The level of inorganic filler ranges from 40 to 80% by weight, preferably from 60 to 70% by weight, based on the weight of dry mixture or aqueous mortar or compound.

The predominant inorganic filler may be calcium carbonate, usually derived from limestone. Other inorganic fillers that may be used include mica, clay, expanded pearlite, and talc.

The dry mix or mortar may be substantially free of other fillers or materials that react with other components of the composition, such as water, especially calcium sulfate hemi-hydrate.

The liquid tape joint compound composition of the present invention may further comprise an emulsion polymer binder formed by an aqueous emulsion polymerization method. The aqueous emulsion polymer may be selected from a variety of synthetic classes such as vinyl acetate polymers, vinyl acetate-acrylic copolymers, vinyl acetate-ethylene copolymers, acrylic polymers, styrene-butadiene copolymers, and blends thereof.

Emulsion polymeric binders can be supplied, for example, as water-redispersible polymer powders resulting from the spray-drying of aqueous emulsion polymers, for use in dry mix compositions in the form of solids, or as aqueous dispersions of polymers.

It is also possible to use other components such as biocides, organic or inorganic thickeners and / or secondary water retainers, sag inhibitors, air entraining agents, wetting agents, antifoaming agents, dispersants, calcium complexing agents, A water repellent agent, a water redispersible polymer powder, a biopolymer, a fiber and a surfactant may be included in the composition of the present invention. All of these other ingredients are known in the art and are available from commercial sources. Such additional additives may also be mixed with the gypsum-free mixture of the present invention.

The pH of any mortar is typically in the range of 3 to 11, preferably in the range of 6 to 8. The viscosity of an aqueous tape joint compound or mortar is typically in the range of 400 to 800 Brabender units ("BU") at 25 캜.

The compositions of the present invention as dry mixes or wet compounds are used as gypsum-smoothing mortars and are very thinly applied to walls, wallboards or to finish on plaster, for example to a thickness of less than 0.5 to 10 or 7 mm .

The composition of the present invention is also used as a tape joint compound and a dry mixture tape joint compound to be mixed with water in use. These are generally applied by hands after mixing with the joint tape on the seat lock (if necessary).

Aqueous tape joint compounds are generally applied to wallboard panels, for example, using a machine tool that simulates the action of a wide knife troweling a tape joint compound, or using a wide knife. The drying is typically allowed to proceed under ambient conditions, for example, at 10 to 40 占 폚.

EXAMPLES The following materials were used.

Dry type gypsum dry powders without cellulose ether (Germany ELEK Casea GmbH, CASUTEC ^TM WS). The cellulose ether was hydroxyethyl methylcellulose available as WALOCEL ^占 MKX 25000 cellulose ether (Dow Wolff Cellulosics GmbH, Germany). Viscosity is shown below.

EXAMPLES 1-4: Incorporation of PCE Superplasticizer over Cellulose Ether :

The wet filter cake of hydroxyethyl methylcellulose (HEMC) was placed in a heated laboratory scale (4-6 liter volume) kneading machine (Coperion Werner & Pfleiderer Masch. Typ .: LUK 4 III-1 in Stuttgart, Germany) And kneaded continuously for 30 minutes at a shear rate of 25 to 50 rpm. The PCE polymer flocculant was added for less than 10 minutes (polymethacrylic acid with polyethylene oxide and methyl endcapped polyethylene oxide ester side chain, Glenium ^TM 51 35 wt% aqueous PCE solution, BASF, Ludwigshafen, Germany). The mixture was kneaded at a shear rate of 25 to 50 rpm for 20 minutes and then the product was dried in a drying cabinet at 55 DEG C and an Alpine mill with a 0.5 mm sieve (Hosokawa Alpine Aktiengesellschaft, Augsburg, Germany) Was milled for a time sufficient to pass the sieve through the sieve to form a dry mix additive. The particle size was then adjusted using a standard sieve such that the product had an average particle size < 63 microns of at least 30 wt.%.

As shown in Table 1 below, the grades of HEMC used and compared had a constant viscosity.

Table 1: Wet Viscosity of the polymeric fluidizing agent cellulose ether mixture

* Viscosity: 2% aqueous solution, Haake Rotovisko RV 100, shear rate 2.55 s ^-1 , 20 ° C

The polyacrylamide not listed in Table 1 above was dry and had a 30 wt% anionic charge and a viscosity of 1600 mPa ((1 wt% concentration in water at 2.51 s ^-1 with 10% NaCl at room temperature) ; This was added to the pulverized cellulose ether dry mixture additive and dry mixed to produce the final additive product. The dry polyacrylamide has the appropriate particle size provided.

Test Method : 200 g dry type gypsum smoothed mortar and joint filler material were dry blended with 1.0 g dry mix additive and mixed in a plastic cup using tap water; The mortar was mixed for 45 seconds using a wooden bar after a waiting time of 15 seconds. Immediately after the stirring, the workability was evaluated as shown in Table 2 below. After a downtime of 10 minutes, the mortar was again stirred and the workability was evaluated as described in Table 2 below. Workability was visually assessed for lump formation. It shows whether the chunk is present and, if so, how much: 1 is the best; 5 is the worst, 2 is the best. The ease of the migration and stirring test refers to the boiling point at which the point is observed to be observed and finally, and after stirring; This is evaluated in comparison with the comparative example, numbers greater than 100 indicate more intense viscosity and less agitation, while numbers less than 100 indicate less significant viscosity.

Table 2: Workability

As shown in Table 2 above, the compositions of Examples 1 to 4 are thicker than the comparative examples and provide easier migration and application. In addition, the more easily the PCE coats the surface of the cellulose ether particles in the dry mix additive, the easier it is to move.

Examples 5 to 10: Polymers into cellulose ethers Incorporation of colloidal stabilizer :

As shown in Table 3 below, the synthesized hydroxyethyl methylcellulose [HEMC; DS (M) = 1.54; A wet filter cake (601 g, 41.1 wt.% Solids content) of MS (HE) = 0.31 was added to a heated kneading machine (Coperion Werner & Pfleiderer Masch. Typ .: LUK 4 III-1 in Stuttgart, Germany) And kneaded for 30 minutes. A 20 wt% aqueous solution of 88% hydrolyzed PVOH (Kuraray Europe GmbH, Mowiol ^TM 4-88 LA, Hartsheim am Main, Germany) was combined within 10 minutes. The mixture was kneaded for 20 minutes, after which the product was dried in a drying cabinet at 55 ° C and 100% by weight of the product was passed through a sieve in an Alpine mill (Hosokawa Alpine Aktiengesellschaft, Augsburg, Germany) with a 0.5 mm sieve And milled for a time sufficient to form a dry mix additive. The particle size was then adjusted using a standard sieve such that the product had an average particle size < 63 microns of at least 30 wt.%.

Table 3: Polymeric Colloidal Stabilizer Composition

* Viscosity - 2% aqueous solution, Haake Rotovisko RV 100, shear rate 2.55 s ^-1 , 20 ° C

The dry cellulose polyacrylamide (not shown in Table 3) (30% by weight anionic charge and 10% NaCl at room temperature, viscosity of 1600 mPa.s at 2.51 s ^-1 at 1 wt% concentration in water) Ether dry mix additive and incorporated into the composition by dry mixing. The dry polyacrylamide has the appropriate particle size provided.

Application test : The composition was tested by forming mortar. In each composition, 800 g of gypsum material was dry blended with 0.5% (solids) polymer additive modified cellulose ether. Adding water to the plastic cup; Dry mortar was then added. Using a standard kitchen mixer (Krups GmbH, Offenbach am Main, Germany), the water / dry components were mixed at low speed for 5 seconds and then immediately for 55 seconds at high speed. After a downtime of 10 minutes, the wet mortar was again mixed at high speed for 15 seconds. Thereafter, a prism was prepared from the composition.

Prism Manufacturing : A mold of expanded polystyrene (EPS) having a rectangular female mold (40 mm x 40 mm x 160 mm) was filled with about half of each mortar and then the filled mold bottom was pressed against a cured flat surface Tapping and compressing by hand or shaking 5 times. The rest of each mold was then filled and shaken again 20 times. Each mold was covered with a polyethylene film and dried. After curing for 2 days, the mortar was removed from the prism and stored again in a PE plastic bag for 5 days. After 5 days, the prism was stored under standard climatic conditions (23 ° C / 50% moisture) for an additional 21 days.

Bending and Compressive Strength Measurement : After curing, three prisms were bent at 0.25 KN / cm2 by Tonitrol Druck und Biegezug Pruefanlage (Bluhm & Feuerherdt GmbH, Berlin, Germany) according to DIN EN 196-1 (2005-05) s strength of flexural strength. Seven pieces from the flexural strength measurement were then used to measure the compressive strength at an intensity of 0.7 KN / s using the same apparatus as in the flexure test to compress the molded prism. The results are shown in Table 4 below.

Table 4: Strength test results

As shown in Table 4 above, the compositions of the present invention improved the flexure and compressive strength of the cured mortar as a function of the amount of the polymeric colloidal stabilizer polymer additive of the present invention. The more additives used, the better the strength, which was much better than the cellulose ether alone.

Claims (10)

A method of making a composition for use as a gypsum dry mixture or gypsum tape joint compound additive,
From 0.1 to 10% by weight, based on the total cellulose ether solids, of a polymeric additive selected from polymeric colloidal stabilizers, polymeric fluidizers, and combinations thereof, based on 60 to 80% water, one or more cellulose ethers, and total cellulose ether solids Kneading the cellulose ether mixture at a high temperature of 50 to 120 DEG C to form an additive;
Drying and pulverizing the additive; And
And then combining said additive with one or more dry polyacrylamides in a total amount of 0.1 to 20% by weight, based on the total cellulose ether solids. The kneading apparatus according to claim 1, wherein the kneading device is an extruder, a kneader, Mixer; A high shear mixer, or a homogenizer. The method according to claim 1, wherein the cellulose ether is hydroxyethyl methylcellulose. The method of claim 1, wherein the amount of the polymer additive is in the range of 0.2 to 5 wt.%, Based on the total cellulosic ether solids. The method of claim 1, wherein the polymer additive is a polymeric colloidal stabilizer that is polyvinyl alcohol. The method of claim 1, wherein the polymer additive is a polymeric colloidal stabilizer present in the mixture as an aqueous composition having 5 to 30 weight percent solids. The method of claim 1, wherein the polymer additive is a polymeric fluidizer selected from a polycarboxylate ether, and a melamine / formaldehyde sulfonate. 8. The method of claim 7, wherein the polymeric fluidizing agent is a polyacrylic acid or polymethacrylic acid ether containing at least one alkyl polyglycol ether side chain. The method of claim 1, wherein the polymer additive is a polymeric fluidizer present in the mixture as an aqueous composition having from 10 to 50 weight percent solids. As a dry mixture composition,
Gypsum or calcium sulfate, and a dry mix additive,
Wherein the dry mix additive comprises at least one cellulose ether powder and wherein the cellulose ether powder comprises from 0.1 to 10% by weight, based on total cellulose ether solids, of a polymeric colloidal stabilizer, a polymeric fluidizer and combinations thereof The selected polymer additive;
Wherein the dry mix additive further comprises a polyacrylamide in an amount of from 0.1 to 20% by weight, based on the total cellulosic ether solids.